1. Field of the Invention
The present invention relates generally to solar generator panels, in particular for space applications. It relates more particularly to a solar generator panel, in particular for spacecraft, including at least one reflector for reflecting solar radiation onto at least one photovoltaic cell of the panel.
2. Description of the Prior Art
A solar generator panel transported in a spacecraft such as a satellite generally includes:                a panel supporting an array of photovoltaic cells forming strings of cells, converting solar energy into electrical energy, and        an array of reflectors that concentrate solar radiation onto the above by means of a coating with adequate properties.        
Solar generator panels of the above kind can be distributed in accordance with highly diverse configurations. Conventionally this means a longitudinal succession, parallel to a direction away from the body of the spacecraft, and about which the generator is adapted to turn to track the Sun. However, providing supplementary lateral panels in addition to the panels previously referred to in order to increase the electrical power available has been proposed. Also known in the art are configurations in which the panels are disposed in a transverse direction, i.e. in a direction transverse to the longitudinal direction previously cited in which the spacer arm or yoke that connects the generator to the body of the spacecraft extends and about which the generator is adapted to turn to track the Sun.
The generator is folded up during launch and its panels are stacked in a configuration known as a stacked or stacking configuration.
Putting the generator into operational service, for example when the vehicle is a satellite that has been placed in its service orbit, imposes unfolding the stack of panels: this is referred to as unstacking.
To change from the stacking configuration to the deployed configuration, in which the solar panels are disposed substantially in the same plane, the panels are articulated in pairs, either by means of hinges having adjacent elements articulated about a pivot axis and each fastened to one of the two adjacent panels or by means of hinges connecting parallel edges of the panels.
With regard to the method of concentrating solar radiation, a system called the bucket system, like the system 1 shown in FIG. 1, was initially proposed and was attractive because of its apparent simplicity of use. It consists in deploying on respective sides of a conventional solar panel 2 two flexible reflectors that geometrically double the surface area collecting solar flux. However, this system suffers from a number of drawbacks, in particular that of the thermal model adopted and most importantly that of having a technological limitation in terms of concentration factor and therefore of power. Furthermore, it appears difficult to hold the reflective films in an optimum configuration, as there is the risk of defects in terms of flatness or rigidity occurring. A supplementary problem is that the impact of defects (holes, creases) in the reflectors produce a non-uniform active surface, leading to the occurrence of phenomena known as “hot spots”: high current variations can surge from one string of cells to another, associated with the nonuniform distribution of the solar flux.
A new concentration concept was then introduced to alleviate the above drawbacks. According to this concept, a generator panel has an alternating succession of strings of cells and reflectors. Thus concentration is effected locally, at the level of the cells, which is why such systems are usually called local concentration systems.
Local concentration systems are described in U.S. Pat. No. 6,177,627, for example, and are shown in FIGS. 2a and 2b of the present application. FIG. 2a shows a triangular section reflector 4 supported by a panel 5. The reflector 4 is formed of a flexible metallic portion 41 covered on two walls that are open toward space by a flexible metallic film 42 able to reflect solar radiation. In the deployed position, as shown in FIG. 2a, the reflector is naturally tensioned, the portion 41 being formed of a material that straightens naturally into an erect position. On the other hand, the facing panels are designed so that when the panels 5 are in their stacked configuration, as shown in FIG. 2b, the space between them is minimized, by compressing the facing reflectors 4 and 4′ to the maximum.
In this constrained position, the surfaces of the two reflectors in contact with each other being those of the reflective films, they may be considerably degraded by rubbing contact and thereafter no longer be able to fulfill their reflective function.
Thus an object of the present invention is to remedy the problems stated hereinabove by proposing a solar generator panel including a reflector whose functional reflective surface cannot be degraded in the stacked configuration, for example by rubbing contact.